Biofouling is a process in which organisms and their by-products encrust a surface. In the case of bacteria, this process leads to the formation of a well-defined bacterial network, termed biofilm. Biofilms provide the bacteria with superior survival properties under exposure to antibiotics. Biofilm formation on medical devices and implants leads to severe infection which may result in patient death.
The attachment of marine organisms to ships and other marine devices is a major issue in the marine industry as organisms such as barnacles and marine mussels form a thick heavy biolayer on the surface of the device. This added weight causes delay in transportation and a higher consumption of fuel. In addition, colonization of ship hulls has been linked to two major environmental pollutions which are emission of gases (CO2, CO, SO2, and NOx) into the atmosphere and the introduction of invasive species to marine habitats.
Other industries using water in their processes, for example cooling towers and turbines, struggle constantly with biofouling buildup and clogging of pipes.
Biofouling initiates with the adsorption of proteins and polysaccharides onto a substrate, therefore many antifouling approaches aim to avoid biofouling by preventing protein adsorption or its degradation. These approaches include both chemical and topographical modification of a surface.
Antifouling materials prevent organisms from attaching to a surface. The challenges in designing such materials are in the ability to synthesize a material that prevents the attachment of the organism to the surface, performing in an authentic environment, and meanwhile does not have an effect on its surrounding environment by releasing toxic molecules. Antifouling materials such as paints and metal nanoparticles prevent the attachment of these organisms to a substrate, but they are toxic and harmful to the environment.
Immobilizing PEG is one of the most commonly used approaches to impart protein resistance to a surface. The antifouling properties of PEG-based coatings have been widely known. The physical adsorption or covalent attachment of PEG chains cannot usually reduce protein adsorption below a certain limit because of steric factors that limit the density of the attached polymer chains. In addition, PEG has a high tendency to undergo autoxidation.
Physical approaches to antifouling include the use of UV and ultrasonication treatments of the substrate.